Metal-drawing die



lPiumini .lune e, 1944 l METAL-,DRAWING Dm Henry G. Keshian, Waterbury, Conn., assigner to Chase Brass & Copper Co. Incorporated, Waterbury, Conn., a corporation l Application May' 1s, 194z,lser1n No. 443,553

zclaitns.v

This invention relates to improvements in metal-drawingV dies, and more particularly to metal-drawing dies having a die-nib ,or insert reinforced by a surrounding reinforcing-ring.

One object of this invention is to provide an improved metal-drawing die formed of a die-nib or insert characterized by heat-resistance and wear-resistance, and surrounded by av reinforcing-ring capable of preventing cracking of the die-nib. With the above and other objects in view, as

' will appear to those skilled in the art from the present disclosure, this invention includes all features in the said disclosure which are' novel over the prior art.

In the' accompanying drawing forming part of the present disclosurefin which one way of carrying out thelnvention is shown for illustrative purposes:

Fig. l is a front elevation of a metal-drawing die made in accordance with the present invention; and f Fig. 2 is a sectional view on line 2-2 of Fig. l. In the description and claims, the various parts "and steps are identified by specific terms for convenience, but they are intended to be as ge- -neric in their application as the .prior art wili permit.

The metal-drawing die Il illustrated in the drawing, is for drawing metal tubes, and includes a die-nib ordie-insert Il formed of ma,-

terial characterized by heat-resistance and wear-resistance, and is preferably formed Yoli high-speed steel characterized by heat-resistance and by being capable of being heat-treated to give'it wear-resistance, and is reinforced lby a reinforcing-ring l2 shrunk upon the die-nib il. The reinforcing-ring I2 is formed of steel characterized by being capable of being heat-treated to give it a combination of substantial elongation and high elastic strength, and is preferably formed of alloy steel characterized by being capable of being heat-treated to give it a combination of substantial ductility or elongation and high elastic strength or elastic limit.

'I'he die-insert I I is preferably formed of high; speed steel having ay high tlmgsten content.

Where such high-speed steel is used, it is hard- A suitable high elastic strength alloy steel for use in making the reinforcing-ring l2, is S. A. E.

steel No. 4340 which when heated to 1500 F. and

quenched in oil 'or otherwise suitably rapidly 5 cooled below its ycritical-hardness temperaturegives it a highV elastic strength or elastic' limit of between 200,000 and 220,000 lbs, per square inch but very. low elongation. The ring is then tempered at a suitable temper-ing temperature l0 such as 1050 F. for about'threc hours to give it a substantial elongation` characteristic or duc tllity.` such, for example, as fromabout l0 to 20% elongation, this tempering treatment reducing the elastic strength to' between 130,000 and 190,000 lbs. per square inch, depending on the tempering temperatureused. The ring is kthen machine-finished to bring its surfaces true to vsize and with the inside diameter of the ring a suitable amount smaller than the outside diamf:

2o eter of the die-insert. The ring is then heated to a temperature not substantially higher than the tempering temperature, and thedie-insert is 'heated to about 400 F. and placed inside oi the ring, and the ring'is permitted to cool and shrink upon the insert and grip the same. In this operation of constructing an adequately-reinforced die-nib or insert, after the ring has been tempered or drawn to increase its ductility, care is taken not to heat the-ring substantially above the tempering or drawing temperature when the rlng is to be shrunk on, the dieinsert. The shrinkage allowance or amount that the inside diameter of the ring is made smaller than the outside diameter of the die-insert, may vary from about oneV and one-quarter to about two and three-quarters thousandths of an inch per inch .of inside diameter of the ring, depending on the` ratio of the outside diameter of the ring to its .-inside diameter. Thus, where these ratiosare one and one-half to'one, the shrinkage allow- `ance would be about one'and one-quarter thousandths per inch of inside diameter of the ring.l

' and where these ratios are two to one, the shrinkage allowance would be about two and one-half thousandths per inch of inside diameter of the ring. IThe limitingfactors in all cases will be.` that the ring must, be tempered at a temperature that will give an elongation of at least about 10% and an elastic limit of at least about 100,000 lbs. per square inch, and that the ring must be heated to a temperature high-enough to permit the die-insert and ring to be telescoped'together but not substantially above the temperingtemperature so as not to substantially lower the u elastic limit produced by the tempering.

' respects as illustrative and The invention may be earned out in other the appended claims are' Y I io` l. A metal-drawing die comprisingza die-nib Y' formed ci' steeihcapable of being hardened by v heat-treatment to give it a combination of high heat-resistance and high wear-resistance, and which 'die-nib has been ygiven said heat-treatment; and a reinforcing-ring shrunk` on. said die`- o nib to reinforce the same; said reinforcing-ring being formed ot steel capable ci being hardened when subjected to' relatively-high-temperature heat-treatment and then rapidly cooledto below its critical-hardness temperature, and capable oi 1 then beinggiven a substantial elongation 'char- 'acteristic andahigh elastic-limit characteristic 'when subjected `to relatively-low-temperature heat-treatment below said critical-hardness temperature,

'on said die-nib, and the said reinand which reinforcing-ring has' been given the said treatments prior to having been shrunk asta-ies forcing-ring having been shrunk on said die-nib whileat an initial temperature not substantially higher than gives the said elongation and elasticlimit characteristics.

2. A metal-drawing die comprising: a die-nib formed of high-speed steel capable of being hardened by heat-treatment to give it a combination of high heat-resistance'and high wearresistance. and which Adie-nib has been given said heat treatment; and a reinforcing-ring shrunk on said die-nib to reinforce the same; said reinforcing-ring being formed oi' alloy steel capable oi being hardened when subjected to relativelyhigh-temperature heat-treatment and then rapidly cooled to below its critical-hardness temperature, and capable of then being given a substantial elongation characteristic and a yhigh elastic-limitl characteristic when subjected to relatively-low-temperature heat-treatment below said critical-hardness temperature, and which reinforcing-ring has been given the'said treatments prior to having been shrunk on said dienib, and the said reinforcing-ring having been shrunk on said die-nib while at an initial temperature not substantially higher than gives the said elongation and elastic-limit characteristics.

HENRY G. rmsHIAN. 

